The goals of this research proposal are a) to test the hypothesis that the transcription factor milieu in adult erythrocytes is supportive of full level expression of the human gamma gene, b) to identify and purify the putative gamma gene trans activators and to test their effects on gamma-globin gene expression in the mouse model. Our specific aims are i) to investigate whether the transcription factor milieu in adult erythrocytes is supportive of full level expression of the human gamma gene. This will be achieved by replacing the minimal promoter of the human beta-globin gene with the counterpart of the gamma-globin gene in the context of the yeast artificial chromosome (YAC) carrying the human beta- globin locus and by testing beta-globin expression driven by the gamma promoter in transgenic mice. The results from these studies will be instrumental for designing a feasible strategy for gamma-globin gene transactivation. ii) to identify and purify a putative trans activator associated with the hereditary persistence of fetal hemoglobin (HPFH) -198 mutation and to test if overexpression of the gene encoding this protein will re-activate the human gamma-globin gene in transgenic mouse model. iii) to identify and purify proteins that are responsible for human gamma-globin gene activation in the adult by using comparative study of the protein binding profiles of the human (activated) and galago(silenced) gamma promoters in the context of the muLCR gamma in transgenic mice. iv) to identify novel TATA box-independent transcription factor(s) that activates gamma gene expression in K562 cells. It is expected that these studies will facilitate the designing of a feasible strategy for human gamma-globin gene transactivation and discover novel gamma- globin gene trans activators. Such a development will have important consequences for the treatment of patients with sickle cell disease or beta thalassemia syndromes.